System and Method for Uplink Timing Synchronization in Conjunction with Discontinuous Reception

ABSTRACT

A system and method are disclosed for providing uplink timing synchronization during DRX operation in a wireless communication system.

RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.12/865,652, filed on Jan. 20, 2011, which is a U.S. National Stage ofPCT/US2009/032591, filed on Jan. 30, 2009, which claims the benefit ofU.S. Provisional Patent Application No. 61/025,485 filed on Feb. 1,2008, the applications are hereby incorporated by reference in theirentirely.

FIELD OF APPLICATION

The application relates to uplink timing synchronization in a wirelesscommunication system.

BACKGROUND

In traditional wireless telecommunications systems, transmissionequipment in a base station transmits signals throughout a geographicalregion known as a cell. As technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This advanced network access equipment mightinclude, for example, an enhanced node-B (eNB) rather than a basestation or other systems and devices that are more highly evolved thanthe equivalent equipment in a traditional wireless telecommunicationssystem. Such advanced or next generation equipment is typically referredto as long-term evolution (LTE) equipment. For LTE equipment, the regionin which a wireless device can gain access to a telecommunicationsnetwork might be referred to by a name other than “cell”, such as “hotspot”. As used herein, the term “cell” will be used to refer to anyregion in which a wireless device can gain access to atelecommunications network, regardless of whether the wireless device isa traditional cellular device, an LTE device, or some other device.

Devices that might be used by users in a telecommunications network caninclude both mobile terminals, such as mobile telephones, personaldigital assistants, handheld computers, portable computers, laptopcomputers, tablet computers and similar devices, and fixed terminalssuch as residential gateways, televisions, set-top boxes and the like.Such devices will be referred to herein as user equipment or UE.

In wireless communication systems, transmission from the network accessequipment (e.g., eNB) to the UE is referred to as a downlinktransmission. Communication from the UE to the network access equipmentis referred to as an uplink transmission. Wireless communication systemsgenerally require maintenance of timing synchronization to allow forcontinued communications. Maintaining uplink synchronization can beproblematic, wasting throughput and/or decreasing battery life of an UEgiven that a UE may not always have data to transmit.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a schematic diagram of a cellular network according to anembodiment of the disclosure;

FIG. 2 is a schematic diagram of a cell in a cellular network accordingto an embodiment of the disclosure;

FIG. 3 is a schematic diagram of a possible uplink transmission channel;

FIG. 4 is a signaling diagram between Network Access Equipment and aUser Equipment;

FIG. 5A is a timing diagram showing a first example of uplink timingreference signal timing having regard to discontinuous reception timing;

FIG. 5B is a timing diagram showing a second example of uplink timingreference signal timing having regard to discontinuous reception timing;

FIG. 6A is a flowchart corresponding to one UE embodiment;

FIG. 6B is a flowchart corresponding to one network access equipmentembodiment;

FIG. 7 is a diagram of a wireless communications system including amobile device operable for some of the various embodiments of thedisclosure;

FIG. 8 is a block diagram of a mobile device operable for some of thevarious embodiments of the disclosure;

FIG. 9 is a block diagram of a software environment that may beimplemented on a mobile device operable for some of the variousembodiments of the disclosure;

FIG. 10 is a block diagram of an exemplary general purpose computeraccording to one embodiment of the present disclosure;

FIG. 11 is an exemplary block diagram of modules in the User Equipment;and

FIG. 12 is an exemplary block diagram of modules in the network accessequipment.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

FIG. 1 illustrates an exemplary cellular network 100 according to anembodiment of the disclosure. The cellular network 100 may include aplurality of cells 102 ₁, 102 ₂, 102 ₃, 102 ₄, 102 ₅, 102 ₆, 102 ₇, 102₈, 102 ₉, 102 ₁₀, 102 ₁₁, 102 ₁₂, 102 ₁₃, and 102 ₁₄ (collectivelyreferred to as cells, 102). As is apparent to persons of ordinary skillin the art, each of the cells 102 represents a coverage area forproviding cellular services of the cellular network 100 throughcommunication from a network access equipment (e.g., eNB). While thecells 102 are depicted as having non-overlapping coverage areas, personsof ordinary skill in the art will recognize that one or more of thecells 102 may have partially overlapping coverage with adjacent cells.In addition, while a particular number of the cells 102 are depicted,persons of ordinary skill in the art will recognize that a larger orsmaller number of the cells 102 may be included in the cellular network100.

One or more UEs 10 may be present in each of the cells 102. Althoughonly one UE 10 is depicted and is shown in only one cell 102 ₁₂, it willbe apparent to one of skill in the art that a plurality of UEs 10 may bepresent in each of the cells 102. A network access equipment 20 in eachof the cells 102 performs functions similar to those of a traditionalbase station. That is, the network access equipments 20 provide a radiolink between the UEs 10 and other components in a telecommunicationsnetwork. While the network access equipment 20 is shown only in cell 102₁₂, it should be understood that network access equipment would bepresent in each of the cells 102. A central control 110 may also bepresent in the cellular network 100 to oversee some of the wireless datatransmissions within the cells 102.

FIG. 2 depicts a more detailed view of the cell 102 ₁₂. The networkaccess equipment 20 in cell 102 ₁₂ may promote communication via atransmitting antenna 27 connected to a transmitter, a receiving antenna29 connected to a receiver, and/or other well known equipment. Similarequipment might be present in the other cells 102. A plurality of UEs 10(10 a, 10 b, 10 c) are present in the cell 102 ₁₂, as might be the casein the other cells 102. In the present disclosure, the cellular systemsor cells 102 are described as engaged in certain activities, such astransmitting signals; however, as will be readily apparent to oneskilled in the art, these activities would in fact be conducted bycomponents comprising the cells.

In each cell, the transmissions from the network access equipment 20 tothe UEs 10 are referred to as downlink transmissions, and thetransmissions from the UEs 10 to the network access equipment 20 arereferred to as uplink transmissions. The UE may include any device thatmay communicate using the cellular network 100. For example, the UE mayinclude devices such as a cellular telephone, a laptop computer, anavigation system, or any other devices known to persons of ordinaryskill in the art that may communicate using the cellular network 100.

The format of an uplink channel is shown schematically in FIG. 3. Theuplink channel is representative of a two dimensional time-frequencyresource, in which frequency is indicated along the vertical axis andtime, in the form of OFDM symbols, slots, sub-frames and frames areindicated on the horizontal axis. The transmission can be one of anumber of different bandwidths (e.g., 1.25, 5, 15, or 20 MHz). In thetime domain, the uplink is broken into frames, sub-frames and slots.Each slot 201 (shown as slots 201 ₁, 201 ₂, . . . , 201 ₁₉, 201 ₂₀,collectively slots 201) is made up of seven orthogonal frequencydivision multiplexed (OFDM) symbols 203. Two slots 201 make up asub-frame 205 (sub-frames 205 ₁, 205 ₂, . . . , 205 ₁₀, collectively aresub-frames 205). A frame is a collection of 10 contiguous sub-frames.Because the exact details of a sub-frame 205 may vary depending upon theexact implementation, the following description is provided as anexample only. The UE will transmit using a constant-amplitude andzero-autocorrelation (CAZAC) sequence so that more than one UE maytransmit simultaneously. The demodulation (DM) reference symbol (RS) isplaced on the fourth symbol 209 of each slot; and a control channel 211is taken up by at least one resource block on the very outside edges ofthe frequency band.

In some embodiments, a sounding reference signal (SRS) is considered tobe an uplink timing reference signal transmission. SRS are madeavailable at the beginning, or end, of each sub-frame 205 and is brokendown into several blocks of 12 sub-carriers (not individually shown)that correspond to the same frequency bandwidth as a resource block. AUE may use one or all of those frequency blocks depending on thetransmission bandwidth selected. The UE may also use every othersub-carrier in one or more multiple frequency blocks. In the illustratedexample, the SRS is shown in the first symbol 207 of the sub-frame 205 ₁and of sub-frame 201 ₁₉. The transmission of SRSs is based on the timebetween subsequent SRS transmission by a single UE. FIG. 3 also showswhere in time and frequency that the physical uplink control channel(PUCCH), which occurs on control channel 211, is placed. Controlsignaling takes place in the PUCCH. In one embodiment, the systemimplements a hybrid automatic repeat request (HARQ) acknowledgement(ACK)/negative acknowledgement (NACK) feedback. An ACK or NACK is senton the PUCCH 211 by the UE to the eNB to indicate whether a packettransmitted from the eNB was received at that UE. A physical uplinkshared channel (PUSCH) is used to send user data.

The above description of the uplink channel is one implementation of anuplink channel. It will be appreciated that other uplink channelconfigurations may be used wherein an uplink timing reference signaltransmission (e.g., SRS) is sent during any portion of the uplinkmessage, not necessarily only at the beginning or end of a specifiedtime interval (e.g., slot).

In order to maintain uplink synchronization, it is desirable for thenetwork access equipment 20 (shown in FIG. 1) to calculate the uplinkchannel conditions by analyzing signals sent from the UE 10. Onepossible signaling diagram of signals sent between the network accessequipment 20 and the UE 10 is shown in FIG. 4. In this embodiment, thenetwork access equipment 20 instructs the UE 10 when to send an uplinktiming reference signal transmission (e.g., SRS), through use of anuplink timing reference signal transmission instruction message 241. Theuplink timing reference signal transmission instruction message 241 mayinclude any one of a variety of instructions. For example, the networkaccess equipment 20 may instruct the UE 10 via the timing referencesignal transmission instruction message 241 to send the timing referencesignal transmissions at a constant rate, or in bursts depending on thevelocity of the UE 10 relative to the network access equipment 20. In aresponse 243, the UE 10 may send the timing reference signaltransmissions (e.g., SRS) in accordance with the instructions of thenetwork access equipment 20.

In order to conserve battery power in the UE the UE may operate withdiscontinuous reception (DRX). Typically, the UE will turn its receptioncapability on and off in a repeating fashion. The network is aware ofthe DRX behavior and makes its transmission to the UE during periodsthat the reception capability is on. An “On” period followed by an “Off”period is a DRX cycle.

DRX in Connected Mode will be configured by the network. Part of theconfiguration is the setting of the DRX-cycle “On” Duration, inactivitytimers and HARQ timer. During the “On” periods (periods the receiver ison each having a length specified by the “On Duration”), the UE willmonitor the PDCCH (packet data control channel) or configured resourcefor the possible downlink transmissions. When a PDCCH is decodedsuccessfully, an inactivity timer will be started. At the end of the“On” period, the UE may go back to sleep according to the DRXconfiguration.

SFAS Transmission During DRX “On” Periods

In a first embodiment, the UE will transmit the SRS (more generally anuplink timing reference signal) only during DRX “On” periods. During DRX“Off” periods, the UE does not transmit SRS. In some embodiments, thisinvolves signalling the UE to transmit the SRS with a desired repetitionperiod, and the UE transmitting the SRS for each repetition period onlyif it occurs during a DRX “On” period. Depending on the alignment orlack of alignment between the SRS repetition period and the DRX “On”periods, there may or may not be SRS repetition periods for which no SRSis transmitted. If the SRS is to be transmitted during each and everySRS repetition period, this will require that the DRX cycle be asfrequent, or more frequent than the desired SRS repetition period.

FIG. 5A shows a simple example of this where the SRS repetition periodis a multiple (in this case the multiple is two) of the DRX cycle. Inaddition, for the example of FIG. 5A the SRS is less frequent than theCQI. Indicated at 800 is DRX timing in which there is a DRX cycle 802that includes a DRX “On” Duration (indicated at 804) and a DRX “Off”Duration. The receiver is alternately turned on for “On” periods havingthe DRX “On” Duration and off for “Off” periods having the DRX “Off”Duration. Indicated at 810 is the CQI timing. The CQI has a CQI period812 that is aligned with the DRX cycle. Specifically, the CQI is sentduring the DRX “On” periods. Indicated at 820 is the timing of the SRS.The SRS has an SRS period 822. In this case, the SRS period 822 isdouble the DRX cycle 802. As such, so long as these cycle durations arein place, the SRS can be sent at the desired SRS period during DRX “On”periods.

SRS Transmission Irrespective of DRX “On” Periods

In some embodiments, the UE makes its SRS transmission irrespective ofDRX in certain conditions. This is particularly appropriate in order tomaintain the uplink time alignment for different UE's with highvelocity. This will allow an SRS period to be established that isshorter than the DRX cycle as might be the case when the DRX cycle isparticularly long, and/or when the SRS period has become particularlyshort due to mobility of the UE.

FIG. 5B shows an example of an SRS period that is smaller than the DRXcycle. As discussed above, this situation may be more common when the UEmoves to the longer DRX cycles. If UL synchronization is to bemaintained even during the longer DRX cycle (for example the 640 ms DRXcycle), then the SRS needs to still be transmitted, and depending on themobility of the UE, it may need to be transmitted at a higher frequencythan the DRX cycle. With reference to FIG. 5B, the DRX timing 800 andCQI timing 810 are the same as in FIG. 5A. In this case, the SRS timing820 has an SRS period 840 that is half that of the CQI period 812, andthat is shorter than the DRX cycle 802. In this case, the UE will needto turn its transmitter on outside the normal DRX “On” periods in orderto be able to transmit all of the SRS transmissions.

Resource Release

In some embodiments, to avoid frequent reassignment or release, aresource is allocated for the UE to transmit the SRS, and this SRSresource is not released when the UE is not transmitting the SRS.

In some embodiments, an uplink timing alignment timer is employed. Thetimer represents the amount of time the UE is expected to be able tomaintain uplink synchronization, after which it can be assumed that theUE should not transmit on the UL. The network transmits a timingalignment update command to the UE each time it computes new uplinktiming based on received SRS from the UE to instruct the UE how toadjust its timing alignment. Once alignment has been lost, the UE willneed to regain alignment when it next needs to transmit.

In some embodiments, the uplink timing alignment timer is run by thenetwork. If no timing alignment update command has been sent within theperiod that the timer is running, then the timer will expire, and it isassumed that alignment is lost. In this event, some or all resources(e.g. CQI, SRS) allocated for UL communication are released. The networkwill inform the UE of when the timer expires.

In another embodiment, the timer may run on the UE in which case thenetwork may inform the UE of the timer value. The timer is reset by thereception of a timing alignment (TA) update command.

Sub-Frame Selection

For the example of FIG. 5A. the CQI and SRS are both transmitted duringDRX “On” Durations, although not necessarily with the same frequency. Inanother embodiment, to further save battery consumption, transmission ofSRS and CQI is configured to be in the same sub-frame whenever feasible.An example of this is shown in FIG. 3 where the CQI 213 is sent in thesame sub-frame 201 ₁ as the SRS 207. For the example of FIG. 5A, thisshould be possible for every SRS transmission since the SRS period istwice that of the CQI period. For the example of FIG. 5B, the SRS andCQI can be transmitted in the same sub-frame for every second SRStransmission.

In some embodiments, for the case where the UF is transmitting SRS onlyduring DRX “On” durations, the CQI is also only transmitted during DRX“On” durations. In some embodiments, for the case where the UE istransmitting SRS irrespective of DRX “On” durations, the CQI is allowedto be transmitted during DRX “On” durations and can be transmittedduring periods that the transmitter has been turned on irrespective ofDRX “On” durations for the purpose of transmitting SRS.

The DTX (discontinuous transmission) periods do not necessarily alignwith the DRX periods. Once the SRS and CQI have been transmitted, thetransmitter can be turned off, even though the receiver may still be on.

Scheduling Request Timing

FIGS. 5A and 5B also each show timing of scheduling requests (SR),generally indicated at 830. A scheduling request is an indication sentby the UE to the base station to request the UL resource. In someembodiments, the UE transmits scheduling requests only during DRX “On”periods. In a further enhancement, the UE transmits scheduling requestsduring a sub-frame that the transmitter is already on to transmit theCQI, the SRS or both. This can occur through network configuration ofthe UE, or at the initiative of the UE. Data may be sent from the UEduring the DRX “On” period.

Combination of Methods

In some embodiments, a combination of the above-described methods isemployed in which sometimes the UE only transmits SRS during DRX “On”periods, referred to hereinafter as a first operational mode, and othertimes the UE transmits SRS irrespective of DRX “On” periods, referred tohereinafter as a second operational mode. FIG. 6A illustrates a flowchart of a specific example of such a method for SRS transmission in aUE 10. The method of FIG. 6A might be executed continuously, or whenthere is a change in SRS period and/or DRX cycle, for example. The SRSperiod may change as a function of mobility of the UE, whereas the DRXcycle may change as a function of level of communications activityinvolving the UE. In block 6A-1, the UE receives an instruction from thenetwork. If the instruction is to operate in the first operational mode(yes path, block 6A-2.), the UE operates in the first operational modeat block 6A-3. If there are no instructions to operate in the firstoperational mode (no path, block 6A-2), a subsequent decision involvesdetermining whether there is an instruction to operate in the secondoperational mode. If the instruction is to operate in the secondoperational mode (yes path, block 6A-4), the UE operates in the secondoperational mode at block 6A-5. More generally, in a first operationalmode, the UE executes block 6A-3 and in a second operational mode, theUE executes block 6A-5. The conditions for executing the first or secondoperational mode may be as described above, or may be different. In someimplementations, only the first operational mode is provided, or onlythe second operational mode is provided.

A flowchart of such an embodiment from the network perspective is shownin FIG. 6B. In block 6B-1 the network determines whether the UE shouldoperate in the first operational mode or the second operational mode.This can be done as a function of mobility of the UE and/or channelutilization to name a few examples. At block 6B-2, the network sends aninstruction to the UE to operate in the determined operational mode.

In order to carry out the above processes, the UE 10 comprises aprocessor capable of performing the above process. For simplicity, thedifferent functions have been broken out into different modules. Thesemodules may be implemented separately or together. Further, thesemodules may be implemented in hardware, software, or some combination.Finally, these modules may reside in different portions of the UEmemory. As illustrated in FIG. 11, the UE processor comprises a receivemodule 801, a determination module 803, and a transmission module 807.The receive module 801 receives a message or messages indicating anoperational mode for SRS transmission. The determination module 803determines the manner of transmitting the SRS having regard to themessage. The determination module informs the transmission module 807 tosend the SRS in accordance with the determination made by thedetermination module 803.

In some embodiments, the UE runs an uplink timing alignment timer asdescribed above in which case the UE further comprises en uplink timingalignment timer module 809. The timer is reset upon receipt of a timingalignment update message by the receive module 801. If the timerexpires, the UE releases the resource used for SRS transmission by thetransmission module 807. In other embodiments, rather than the UErunning a timer, the receive module 801 of the UE receives aninstruction from the network that indicates timing has been lost inwhich case the UE releases the resource used for SRS transmission.

Referring now to FIG. 12, the network access equipment 20 also comprisesa processor. The processor comprises a receive module 901, an evaluationmodule 903 and a transmission module 905. Again, these modules aredefined for simplicity, and may be executed in software, hardware,firmware, or both. Additionally, these modules may be stored in the sameor different memories. The receiver module 901 receives SRS messages,CQI and other signals from the UE. The evaluation module 903 evaluatesan appropriate DRX period and a desired SRS period. This may for examplebe done having regard to the activity of the UE, the mobility of the UE,and/or activity of the UE. The evaluation module determines anappropriate SRS transmission behavior having regard to the DRX behaviorand SRS repetition period and instructs the transmission module 905 tosignal this to the UE.

In some embodiments, the network runs an uplink timing alignment timeras described above in which case the processor further comprises anuplink timing alignment timer module 907. The timer is reset upontransmission of a timing alignment update message by the transmissionmodule 905. In one embodiment, if the timer expires, the network sendsan instruction to the UE to release the resource used for SFAStransmission, and the network also releases the resource used for SRStransmission. In another embodiment, if the timer expires, the networkreleased the resource used for SRS transmission without sending amessage to the U. In this second embodiment, the network may havepreviously sent a timer value to the UE. Because the UE may have usedthat timer value to start its own uplink alignment timer, the UE wouldnot need a message from the network informing the UE that the timer hadexpired and the SRS resource is to be released.

FIG. 7 illustrates a wireless communications system including anembodiment of the UE 10. The UE 10 is operable for implementing aspectsof the disclosure, but the disclosure should not be limited to theseimplementations. Though illustrated as a mobile phone, the UE 10 maytake various forms including a wireless handset, a pager, a personaldigital assistant (PDA), a portable computer, a tablet computer, or alaptop computer. Many suitable devices combine some or all of thesefunctions. In some embodiments of the disclosure, the UE 10 is not ageneral purpose computing device like a portable, laptop or tabletcomputer, but rather is a special-purpose communications device such asa mobile phone, a wireless handset, a pager, a PDA, or atelecommunications device installed in a vehicle. In another embodiment,the UE 10 may be a portable, laptop or other computing device. The UE 10may support specialized activities such as gaming, inventory control,job control, and/or task management functions, and so on.

The UE 10 includes a display 402. The UE 10 also includes atouch-sensitive surface, a keyboard or other input keys generallyreferred as 404 for input by a user. The keyboard may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY, andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include a trackwheel, an exit or escape key, a trackball, and other navigational orfunctional keys, which may be inwardly depressed to provide furtherinput function. The UE 10 may present options for the user to select,controls for the user to actuate, and/or cursors or other indicators forthe user to direct.

The UE 10 may further accept data entry from the user, including numbersto dial or various parameter values for configuring the operation of theUE 10. The UE 10 may further execute one or more software or firmwareapplications in response to user commands. These applications mayconfigure the UE 10 to perform various customized functions in responseto user interaction. Additionally, the UE 10 may be programmed and/orconfigured over-the-air, for example from a wireless base station, awireless access point, or a peer UE 10.

Among the various applications executable by the UE 10 are a webbrowser, which enables the display 402 to show a web page. The web pagemay be obtained via wireless communications with a wireless networkaccess node, a cell tower, a peer UE 10, or any other wirelesscommunication network or system 400. The network 400 is coupled to awired network 408, such as the Internet. Via the wireless link and thewired network, the UE 10 has access to information on various servers,such as a server 410. The server 410 may provide content that may beshown on the display 402. Alternately, the UE 10 may access the network400 through a peer UE 10 acting as an intermediary, in a relay type orhop type of connection.

FIG. 8 shows a block diagram of the UE 10. While a variety of knowncomponents of UEs 10 are depicted, in an embodiment a subset of thelisted components and/or additional components not listed may beincluded in the UE 10. The UE 10 includes a digital signal processor(DSP) 502 and a memory 504. As shown, the UE 10 may further include anantenna and front end unit 506, a radio frequency (RF) transceiver 508,an analog baseband processing unit 510, a microphone 512, an earpiecespeaker 514, a headset port 516, an input/output interface 518, aremovable memory card 520, a universal serial bus (USB) port 522, ashort range wireless communication sub-system 524, an alert 526, akeypad 528, a liquid crystal display (LCD), which may include a touchsensitive surface 530, an LCD controller 532, a charge-coupled device(CCD) camera 534, a camera controller 536, and a global positioningsystem (GPS) sensor 538. In an embodiment, the UE 10 may include anotherkind of display that does not provide a touch sensitive screen. In anembodiment, the DSP 502 may communicate directly with the memory 504without passing through the input/output interface 518.

The DSP 502 or some other form of controller or central processing unitoperates to control the various components of the UE 10 in accordancewith embedded software or firmware stored in memory 504 or stored inmemory contained within the DSP 502 itself. In addition to the embeddedsoftware or firmware, the DSP 502 may execute other applications storedin the memory 504 or made available via information carrier media suchas portable data storage media like the removable memory card 520 or viawired or wireless network communications. The application software maycomprise a compiled set of machine-read able instructions that configurethe DSP 502 to provide the desired functionality, or the applicationsoftware may be high-level software instructions to be processed by aninterpreter or compiler to it configure the DSP 502.

The antenna and front end unit 506 may be provided to convert betweenwireless signals and electrical signals, enabling the UE 10 to send andreceive information from a cellular network or some other availablewireless communications network or from a peer UE 10. In an embodiment,the antenna and front end unit 506 may include multiple antennas tosupport beam forming and/or multiple input multiple output (MIMO)operations. As is known to those skilled in the art, MIMO operations mayprovide spatial diversity which can be used to overcome difficultchannel conditions and/or increase channel throughput. The antenna andfront end unit 506 may include antenna tuning and/or impedance matchingcomponents. RF power amplifiers, and/or low noise amplifiers.

The RE transceiver 508 provides frequency shifting, converting receivedRF signals to baseband and converting baseband transmit signals to RE.In some descriptions a radio transceiver or RE transceiver may beunderstood to include other signal processing functionality such asmodulation/demodulation, coding/decoding, interleaving/deinterleaving,spreading/despreading, inverse fast Fourier transforming (IFFT)/fastFourier transforming (FFT), cyclic prefix appending/removal, and othersignal processing functions. For the purposes of clarity, thedescription here separates the description of this signal processingfrom the RF and/or radio stage and conceptually allocates that signalprocessing to the analog baseband processing unit 510 and/or the DSP 502or other central processing unit. In some embodiments, the RFTransceiver 508, portions of the Antenna and Front End 506, and theanalog baseband processing unit 510 may be combined in one or moreprocessing units and/or application specific integrated circuits(ASICs).

The analog baseband processing unit 510 may provide venous analogprocessing of inputs and outputs, for example analog processing ofinputs from the microphone 512 and the headset 516 and outputs to theearpiece 514 and the headset 516. To that end, the analog basebandprocessing unit 510 may have ports for connecting to the built-inmicrophone 512 and the earpiece speaker 514 that enable the UE 10 to beused as a cell phone. The analog baseband processing unit 510 mayfurther include a port for connecting to a headset or other hands-freemicrophone and speaker configuration. The analog baseband processingunit 510 may provide digital-to-analog conversion in one signaldirection and analog-to-digital conversion in the opposing signaldirection. In some embodiments, at least some of the functionality ofthe analog baseband processing unit 510 may be provided by digitalprocessing components, for example by the DSP 502 or by other centralprocessing units.

The DSP 502 may perform modulation/demodulation, coding/decoding,interleaving/deinterleaving, spreading/despreading, inverse fast Fouriertransforming (IFFT)/fast Fourier transforming (FFT), cyclic prefixappending/removal, and other signal processing functions associated withwireless communications. In an embodiment, for example in a codedivision multiple access (CDMA) technology application, for atransmitter function the DSP 502 may perform modulation, coding,interleaving, and spreading, and for a receiver function the DSP 502 mayperform despreading, deinterleaving, decoding, and demodulation. Inanother embodiment, for example in an orthogonal frequency divisionmultiplex access (OFDMA) technology application, for the transmitterfunction the DSP 502 may perform modulation, coding, interleaving,inverse fast Fourier transforming, and cyclic prefix appending, and fora receiver function the DSP 502 may perform cyclic prefix removal, fastFourier transforming, deinterleaving, decoding, and demodulation. Inother wireless technology applications, yet other signal processingfunctions and combinations of signal processing functions may beperformed by the DSP 502.

The DSP 502 may communicate with a wireless network via the analogbaseband processing unit 510. In some embodiments, the communication mayprovide Internet connectivity, enabling a user to gain access to contenton the Internet and to send and receive e-mail or text messages. Theinput/output interface 518 interconnects the DSP 502 and variousmemories and interfaces. The memory 504 and the removable memory card520 may provide software and data to configure the operation of the DSP502. Among the interfaces may be the USB interface 522 and the shortrange wireless communication sub-system 524. The USB interface 522 maybe used to charge the UE 10 and may also enable the UE 10 to function asa peripheral device to exchange information with a personal computer orother computer system. The short range wireless communication sub-system524 may include an infrared port, a Bluetooth interface, an IEEE 802.11compliant wireless interface, or any other short range wirelesscommunication sub-system, which may enable the UE 10 to communicatewirelessly with other nearby mobile devices and/or wireless basestations.

The input/output interface 518 may further connect the DSP 502 to thealert 526 that, when triggered, causes the UE 10 to provide a notice tothe user, for example, by ringing, playing a melody, or vibrating. Thealert 526 may serve as a mechanism for alerting the user to any ofvarious events such as an incoming call, a new text message, and anappointment reminder by silently vibrating, or by playing a specificpre-assigned melody for a particular caller.

The keypad 528 couples to the DSP 502 via the interface 518 to provideone mechanism for the user to make selections, enter information, andotherwise provide input to the UE 10. The keyboard 528 may be a full orreduced alphanumeric keyboard such as QWERTY, Dvorak, AZERTY andsequential types, or a traditional numeric keypad with alphabet lettersassociated with a telephone keypad. The input keys may include a trackwheel, an exit or escape key, a trackball, and other navigational orfunctional keys, which may be inwardly depressed to provide furtherinput function. Another input mechanism may be the LCD 530, which mayinclude touch screen capability and also display text and/or graphics tothe user. The LCD controller 532 couples the DSP 502 to the LCD 530.

The CCD camera 534, if equipped, enables the UE 10 to take digitalpictures. The DSP 502 communicates with the CCD camera 534 via thecamera controller 536. In another embodiment, a camera operatingaccording to a technology other than Charge Coupled Device cameras maybe employed. The GPS sensor 538 is coupled to the DSP 502 to decodeglobal positioning system signals, thereby enabling the UE 10 todetermine its position. Various other peripherals may also be includedto provide additional functions, e.g., radio and television reception.

FIG. 9 illustrates a software environment 602 that may be implemented bythe DSP 502. The DSP 502 executes operating system drivers 604 thatprovide a platform from which the rest of the software operates. Theoperating system drivers 604 provide drivers for the wireless devicehardware with standardized interfaces that are accessible to applicationsoftware. The operating system drivers 604 include applicationmanagement services (“AMS”) 606 that transfer control betweenapplications running on the UE 10. Also shown in FIG. 9 are a webbrowser application 608, a media player application 610, and Javaapplets 612. The web browser application 608 configures the UE 10 tooperate as a web browser, allowing a user to enter information intoforms and select links to retrieve and view web pages. The media playerapplication 610 configures the UE 10 to retrieve and play audio oraudiovisual media. The Java applets 612 configure the UE 10 to providegames, utilities, and other functionality. A component 614 might providefunctionality related to the present disclosure.

The UEs 10, ENBs 20, and central control 110 of FIG. 1 and othercomponents that might be associated with the cells 102 may include anygeneral-purpose computer with sufficient processing power, memoryresources, and network throughput capability to handle the necessaryworkload placed upon it. FIG. 10 illustrates a typical, general-purposecomputer system 700 that may be suitable for implementing one or moreembodiments disclosed herein. The computer system 700 includes aprocessor 720 (which may be referred to as a central processor unit orCPU) that is in communication with memory devices including secondarystorage 750, read only memory (ROM) 740, random access memory (RAM) 730,input/output (I/O) devices 710, and network connectivity devices 760.The processor may be implemented as one or more CPU chips.

The secondary storage 750 is typically comprised of one or more diskdrives or tape drives and is used for non-volatile storage of data andas an over-flow data storage device if RAM 730 is not large enough tohold all working data. Secondary storage 750 may be used to storeprograms which are loaded into RAM 730 when such programs are selectedfor execution. The ROM 740 is used to store instructions and perhapsdata which are read during program execution. ROM 740 is a non-volatilememory device which typically has a small memory capacity relative tothe larger memory capacity of secondary storage. The RAM 730 is used tostore volatile data and perhaps to store instructions. Access to bothROM 740 and RAM 730 is typically faster than to secondary storage 750.

I/O devices 710 may include printers, video monitors, liquid crystaldisplays (LCDs), touch screen displays, keyboards, keypads, switches,dials, mice, track balls, voice recognizers, card readers, paper tapereaders, or other well-known input devices.

The network connectivity devices 760 may take the form of modems, modembanks, ethernet cards, universal serial bus (USB) interface cards,serial interfaces, token ring cards, fiber distributed data interface(FDDI) cards, wireless local area network (WLAN) cards, radiotransceiver cards such as code division multiple access (CDMA) and/orglobal system for mobile communications (GSM) radio transceiver cards,and other well-known network devices. These network connectivity 760devices may enable the processor 720 to communicate with an Internet orone or more intranets. With such a network connection, it iscontemplated that the processor 720 might receive information from thenetwork, or might output information to the network in the course ofperforming the above-described method steps. Such information, which isoften represented as a sequence of instructions to be executed usingprocessor 720, may be received from and outputted to the network, forexample, in the form of a computer data signal embodied in a carrierwave.

Such information, which may include data or instructions to be executedusing processor 720 for example, may be received from and outputted tothe network, for example, in the form of a computer data baseband signalor signal embodied in a carrier wave. The baseband signal or signalembodied in the carrier wave generated by the network connectivity 760devices may propagate in or on the surface of electrical conductors, incoaxial cables, in waveguides, in optical media, for example opticalfiber, or in the air or free space. The information contained in thebaseband signal or signal embedded in the carrier wave may be orderedaccording to different sequences, as may be desirable for eitherprocessing or generating the information or transmitting or receivingthe information. The baseband signal or signal embedded in the carrierwave, or other types of signals currently used or hereafter developed,referred to herein as the transmission medium, may be generatedaccording to several methods well known to one skilled in the art.

The processor 720 executes instructions, codes, computer programs,scripts which it accesses from hard disk, floppy disk, optical disk(these various disk-based systems may all be considered secondarystorage 750), ROM 740, RAM 730, or the network connectivity devices 760.While only one processor 720 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as executed by aprocessor, the instructions may be executed simultaneously, serially, orotherwise executed by one or multiple processors.

RAN1 and RAN2 are standards related to Radio Layer 1 and Radio Layer 2,respectively. Radio Layer 1 generally pertains to, but is not limitedto, the physical layer of the radio interface for UE, UTRAN (UMTSTerrestrial Radio Access Network), Evolved UTRAN, and beyond and maycover both frequency divisional duplex (FDD) and time divisional duplex(TDD) modes of radio interface, Radio Layer 2 generally pertains to, butis not limited to, radio interface architecture and protocols such asmedia access control (MAC), radio link control (RLC) and packet dataconvergence protocol (PDCP), specification of the Radio Resource Controlprotocol, and strategies of Radio Resource Management and the servicesprovided by the physical layer to the upper layers).

Several contributions in RAN2 are considering configurations of CQIreports during DRX. The contributions are also considering what shouldhappen to signaling resources when timing alignment is lost on theuplink. These contributions have not taken fully into consideration therole of sounding reference signals (SRS) and scheduling request (SR) andscheduling indicators (SRI).

It has been agreed in RANI that SRS periods will be 2, 5, 10, 20, 40,80, 160, 320 ms. SRS is used in support of CQI and uplink timingestimation by a base station. RAN2 has introduced as a discussion pointhow to operate CQI while a mobile has been configured for DRX.

In some embodiments, as described above, DRX in Connected Mode will beconfigured by the eNB. Part of the configuration is the setting of theDRX-cycle “On” Duration, inactivity timers and HARQ timer. During the“On” Duration, UE will monitor the PDCCH or configured resource for thepossible downlink transmissions. When a PDDCCH is decoded successfully,an inactivity timer will be started. At the end of the active period, UEmay go back to sleep according to the configurations.

In some embodiments, a length of long DRX cycle is a determiner in howto allow the UE to move into an unsynchronized state. It is conceivablethat a DRX cycle greater than 1 second could lead to loss of ULsynchronization. At such a point, all SRS and CQI transmissions on theUL should be terminated and the UE should access the random accesschannel (RACH) whenever data needs to flow in the UL. In someembodiments, mobility has a direct impact on UL synchronization loss. Ifthe unsynchronized state has not been entered, the SRS transmission mustcontinue as needed. Under modest mobility conditions (e.g. 30kilometers/hour), the SRS period may be on the order of 50 ms. This isless than several of the shorter DRX cycles. Synchronization is to bemaintained if any uplink transmissions are to take place.

In some embodiments, the UE will transmit the SRS during the appropriate“On” Duration. In the “Off” Duration, the UE may not transmit SRS.Furthermore, to simplify the procedure by avoiding frequent reassignmentor release, the SRS resource should not be released when the UE is nottransmitting the SRS. In some embodiments, the SRS resource is onlyreleased when an uplink timing alignment timer expires.

In some embodiments, the UE transmits the SRS during the DRX “On”Duration, and SRS transmissions may be stopped during the off duration.The resource for the SRS is maintained during the DRX and released onlywhen the uplink timing alignment timer has expired.

In some embodiments, as a matter of saving battery power, transmissionof SRS and CQI occur in the same sub-frame whenever feasible. Also, inorder to maintain the uplink time alignment for different UE's with highvelocity, the eNB is enabled to configure the UE for the SRStransmission irrespective of DRX in certain conditions.

In some embodiments, transmission of SRS and CQI is in the samesub-frame whenever feasible to save UE's battery power. To maintainuplink timing alignment, the eNB configures the UE to transmit SRSirrespective of the DRX.

FIG. 5A shows the case when the SRS period is less frequent than CQI.FIG. 5B shows the opposite case. In FIG. 5B the eNB selects an SRStransmission periodicity that is smaller than the DRX cycle. Thissituation will be more common when the UE moves to the longer DRXcycles. If UL synchronization must be maintained even during the longerDRX cycle, for example 640 ms or more, then the SRS is transmitted.

In some embodiments, methods and devices described herein are for use inlong term evolution (LTE) networks. However, the devices and methodsdescribed herein are not intended to be limited to only LTE networks. Insome embodiments, the methods and devices described herein are for usewith other types of communication networks.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

1. (canceled)
 2. A method in a network access equipment, comprising: configuring a discontinuous reception (DRX) mode for a user device; configuring at least one of a first sounding reference signal (SRS) mode and a second SRS mode for the user device; receiving an SRS during a DRX active time when the first SRS mode is used; and receiving an SRS irrespective of the DRX active time when the second SRS mode is used.
 3. The method of claim 2, further comprising sending an instruction to the user device to activate the second SRS mode.
 4. The method of claim 2, wherein the DRX cycle is determined based on a level of communication activity of the user device.
 5. The method of claim 2, further comprising determining a SRS repetition period for the user device to transmit the SRS.
 6. The method of claim 2, further comprising maintaining a resource configuration for the user device to transmit the SRS when not in the DRX active time.
 7. The method of claim 6, further comprising transmitting a SRS configuration element to the user device, the SRS configuration element including the resource configuration for the user device to transmit the SRS.
 8. The method of claim 6, further comprising releasing the resource configuration for the user device to transmit the SRS at the expiration of a time alignment timer.
 9. The method of claim 2, further comprising determining a DRX cycle for the user device.
 10. A network access equipment for a wireless telecommunications system, comprising: a receiver; and a processor, the processor configured to perform operations comprising: configuring a discontinuous reception (DRX) mode for a user device; configuring at least one of a first sounding reference signal (SRS) mode and a second SRS mode for the user device; controlling the receiver to receive an SRS during a DRX active time when the first SRS mode is used; and controlling the receiver to receive an SRS irrespective of the DRX active time when the second SRS mode is used.
 11. The network access equipment of claim 10, wherein the processor is further configured to control a transmitter to send an instruction to the user device to activate the second SRS mode.
 12. The network access equipment of claim 10, wherein the DRX cycle is determined based on a level of communication activity of the user device.
 13. The network access equipment of claim 10, wherein the processor is further configured to determine a SRS repetition period for the user device to transmit the SRS.
 14. The network access equipment of claim 10, wherein the processor is further configured to maintain a resource configuration for the user device to transmit the SRS when not in the DRX active time.
 15. The network access equipment of claim 14, wherein the processor is further configured to controlling a transmitter to transmit a SRS configuration element to the user device, the SRS configuration element including the resource configuration for the user device to transmit the SRS.
 16. The network access equipment of claim 14, wherein the processor is further configured to release the resource configuration for the user device to transmit the SRS at the expiration of a time alignment timer.
 17. The network access equipment of claim 10, wherein the processor is further configured to determine a DRX cycle for the user device. 